PHP MySQL Basic Connectivity Code

<?php
 
//database
$const['sql_username']='mysql_user';
$const['sql_password']='mysql_password';
$const['sql_host'    ]='localhost';
$const['sql_database']='wp_database';
 
function connection()
{
  global $const;
    $user   = $const['sql_username'];
    $pass   = $const['sql_password'];
    $host   = $const['sql_host'    ];
    $dbname = $const['sql_database'];
    $db  = mysql_pconnect($host, $user, $pass) or die("could not connect: " . mysql_error());
    mysql_select_db($dbname, $db) or die("cannot select db $dbname: " . mysql_error());
    return $db;
}
 
$productid=34;
$category ='hardware';
 
$db    = connection();
$query = sprintf("select id,productname,desc,price from products where id=%s and category=%s",
        mysql_real_escape_string($productid),
        mysql_real_escape_string($category)
    );
 
$result = mysql_query($query, $db) or die('could not execute query: ' . $query);
echo "<table>";
while ($row = mysql_fetch_assoc($result))
{
    echo "<tr>";
    echo   "<td>".$row['id']."</td>";
    echo   "<td>".$row['productname']."</td>";
    echo   "<td>".$row['description']."</td>";
    echo   "<td>".$row['price']."</td>";
    echo "</tr>";
}
echo "</table>";
 
?>